Positive grid oscillator



J. w. McNALl. ErAL POSITIVE GRID OSCILLATOR Nov. 23, 1948.

3 Sheets-Sheet l Filed April 13. 1944 INVENTORS .IM ,vf/wuz 9- I. HID/GNov. 23, 1948. J. w. McNALl. ETAL PosITIvE GRIDy oscILLAToR med April1:5, 1944' s suma-snm z ATTORNEY Nov. 23, 1948. J. w. McNALl. Erm.

POSITIVE GRID OSCILLATOR Filed April 15. 1944 1' Shoots-Sheet 3 ,um hmArroRNEY Patented Nov. 23, 1948 POSITIVE GRID OSCILLATOB John W. McNall,East Orange, and Alfred H.

Laidig, Bloomfield, N. J., assignors to Westinghouse ElectricCorporation,` East Pittsburgh, P a., a corporation of PennsylvaniaApplication April-13, 19,44, Serial No. 530,890

s claims. 1

'rms invention relates to positive-grid oscu-v lators, also known asretarding field oscillators, and is directed to structural features ofsuch an oscillator of .particular applicability in the more genericdisclosure of concurrently filed application of co-inventor herein J.W.McNall, Serial No. 530,889, filed April 13, 1944. j

Electrode spacing having commensurate relation to electron transitdistance between the phase `shifts of the oscillation period, introducesproblems of mounting, fabrication, adjustment, tuning,` and so forth,not encountered in usual oscillators, especially when the period ofoscillation chosen is in the ultra high frequency range. Broadly, thepresent invention is directedA to the -solution of the several problemsenumerated.

More specically, an object of the invention is to provide a hollow bodyresonant cavity positivegrid oscillator.

4 Another object of the invention is to provide for a grid betweencathode and anode each elec-I trically a part with the resonator wallbut, as to D. C. potential, electrically separate from either cathode oranode.

'A further object of -the invention is to provide a resonator the wallof which, together with the cathode, anode and positive grid willconstitute a self-contained oscillatory circuit capable of hav- 2 matephysical and electrical relation of electrodes;

Figure 4 is a longitudinal sectional view of a hollow body resonantcavity positive-slid oscilmodied construction of hollow body resonant.

lator which is tunable and wherein all electrodes are insulated forseparate application thereto o! D. C. potentials;

Figure 5 is a plan of Figure 4;

Figure 6 shows diagrammatically the approximate physical and electricalrelation of electrodes of the construction of Figure 4; Y

Figurev 'l is a longitudinal section of af further iustrated 1n saiddrawing and giving attention ining a D. C. potential on' the positivegrid diifering from that on the cathode and anode.`

Yet another object of the invention is to prol vide in a resonant cavityconstruction` of tube, a

positive -grld rigidly mounted and accurately spaced lbetween a closelyspaced cathode and vselector grid. v r

A still .further object of the invention is to provide for adjusting thespacings of cathode to posi- 4 tive grid, selector grid to positive gridand anode yrecitation thereof and by inference from the context.

Referring to the accompanying drawings in which like numerals ofreference lindicate similar parts throughout the several views:

Figure 1 is alongitudinal sectional view of aV hollow body resonantcavity positive-gridoscillator embodying tion;

Figure 2 is a cross-section thereof on line II-II;

. Figure 3 shows diagrammatically the approxithe broad concept of ourinvenitially to Figures 1 to 3, a hollow body resonantcavitypositive-grid oscillator is shown wherein the hollow body l5 isall metal and constituted as a cylindrical outer wall I6' havingdisc-like end walls Il and i8 sealed at theends of the cylindrical wall.At the mid-part of and sealed to said end walls are collars I9, .20,respectively, which are re-entrant in the sense that they project intovthe hollow bodyv coaxially therewith, so their inner `ends are directedtoward each other within the body, said ends being parallel to eachother and to the end walls of the resonator. Said collars each have apart thereof,'which may be termed an extension of the collar, whichprojects outwardly from the end wall of the resonator, each saidextension having an, appropriate seal therebeyond for maintaininginternal vacuum in the y resonator and collars.

` disc;shaped 'and with the axis of the disc coaxial to the axis of thecollar and resonator body, thereby positioning the emitting surfacetransverse to that axis. The body of the cathode is a metallic hollow-body of revolution and consists of a cap portion of cup shape, theclosed end of which constitutes the aforementioned disc-shaped part ofthe cathode andv at the periphery of which is a cylindrical ange 22.Said flange nts over and is secured to a cylindrical head 23 of ahousing portion having a cylindrical torso 24 from the other end ofwhich legs 2i project. The head 23 approximates the diameter of there-entrant collar I9, whereas the torso 24 is of less diameter and thelegs 25 spread to engage the inside of said collar and are spot weldedor otherwise secured thereto. The inside of said collar I9 may beprovided with a forwardly directed shoulder 26 for engagement by theends of said legs 25, thereby serving to locate the cathode emittingsurface precisely parallel to the said shoulder, which is in turnparallel to the end of said collar.

'I'his cathode structure is part of the wall of a resonant cavity, andthe provisionof head 22 substantially the same diameter as collar I9 andseparated therefrom by only a narrow peripheral gap, obtains virtualcontinuity of surface for high frequency oscillation and negligibleimpedance thereto across the gap, The structure, on the other hand has atendency to prevent heat flow from the cathode to said collar, aiding,therefore in maintaining desired cathode temperature. 'I'his samecathode construction is employed likewise in the other tubeconstructions hereinafter described.

A heater filament 21 is shown within the cathode body, said filamentbeing mounted on lead-in wires 28 which extend to the exterior through aglass press 29 formed as part of a re-entrant glass stem 30. The rim ofsaid stem is sealed to the end margin of a suitable metallic ring 3I,the other end margin of which is secured, as by welding, to the marginof the end of the collar I9 protruding from the resonator body. Ring 3Iis of material having substantially the same coeiiicient of expansion asthe glass, a material manufactured under the trade name Kovar, inaccordance with disclosure in Patent 2,062,335 of December 1, 1936, toHoward Scott, being the one preferred.

The other collar 20 is shown as having a grid 32 across the inner endthereof, this grid being distinguished herein from subsequentlydescribed grid by referring to it as the selector grid. Said selectorgrid is parallel to the cathode emitting surface and otherwise fulfillsthe requirements therefor as explained at length in said concurrentlyfiled application.

Within said collar 20, spaced from the wall thereof and spaced from andparallel to said selector grid 32 is an electrode 33, which in thefigure being described, is utilized as an anode. As here shown, saidelectrode 33 is in the form of a disc coaxial with the axis of thecollar and resonator body and has a metallic stem 34 extendinglengthwise of the collar and projecting from the outer end thereof forlead-in purposes. A domelike glass seal 35 is sealed to the stem 34 nextthe outer end thereof, the rim of the dome being sealed to a ring 36 inturn sealed, as by welding, to the said collar. Ring 36 may convenientlybe a duplicate in size and material of ring 3I at the cathode end of thedevice.

In parallelism to and between the aforementioned selector grid andcathode, is another planar grid 31, herein distinguished for referencepurposes by the appellation thereto of the title of positive grid. Thispositive grid 31 extends outwardly beyond the cylindrical region betweensaid cathode and selector grid and toward the cylindricalwall I 6 of theresonator body. A plurality of supporting prongs or wires 38 projectradially inwardly through said wall in the plane to said positive gridand have soldered orother attachment to said positive grid so as torigidly mount the same in place. Said wires or prongs 38 are coaxiallysealed, as `by glass beads 39, within tubes 40 soldered or otherwisesecured in appropriate holes in the said cylindrical wall. Thisccnstruction affords adequate insulation and support for the grid and.also provides a vacuum seal f orthe hole and Wire.` One of said wiresmay be utilized as an electrical connection for application ofdesiredpotential to the said positive grid. To prevent highfrequency radiationfrom leaking out by way of said wires, a suitable choke 4I is applied toeach. i

Capacity coupling between the positive grid and the resonator wall forhigh frequency conduction continuity and for rendering the chamberresonant is provided in the form of cylindrical shells 42 spaced fromthe walls of the resonator body, a distance adequate to prevent passageof D. C. potential. These shells are coaxial with the resonatorcylindrical wall and have inturned flanges 43 next the positive grid,said flanges being juxtaposed upon and secured to the said grid. Supportfor the said shells is obtained by the same radially disposed wires 38,which support the attached positive grid. From the construction shown ofparallel and close association of cylindrical shells 42 to thecylindrical resonator wall I6, continuity for high frequency oscillationis provided and at the same time discontinuity for D. C. current flow isobtained. A coaxial line output 44 the center conductor of which loopsinto the resonator chamber is provided as usual with hollow body highfrequency resonators.

Electrode spacing and connections are dealt with more fully in the saidconcurrent application, for use of the device as a positive gridoscillator. Suffice it to say herein that, as indicated by Figure 3, thespacing of the several electrodes is related to electron transit timeand here shown as such that an electron may travel from cathode 2I topositive grid 31 and from positive grid 31 to selector grid 32substantially in the time required for oscillating phase shift of 180each. Also spacing of the anode from selector grid 32 is substantially adistance representing transit time of an electron therebetween during aphase shift so the electron makes the round trip from said selectorgrid, to the anode and back to the selector grid during substantially aoscillating phase shift. Because of the metallic continuity from cathodemounting to selector grid mounting, those electrodes are shown in Figure3 as connected. Other relationships and character of electrodes may,however, be provided as l found desirable or to carry out the operationof the device in any manner, such as described in said concurrently ledapplication.

While Figures 1 to 3 illustrate the fundamental inventive concept, it isWithin the scope of the invention to vary the spacings and electricalconnections of the electrodes as found desirable. Furthermore, it may bestated that the electrode referred to herein as the anode occupies theposition usually ascribed to an anode, and the term is thus used todistinguish it from other electrodes without restriction as to thefunctioning thereof. Said anode may be utilized for receiving electrons,may be utilized for reflecting primary electrons. or may be used to emitsecondary electrons, and to indicate more definitely this inclusivecharacterization, may be more generally referred to as anelectron-pulling electrode.

In Figures 4 to' 6, structure embodying the invention is shown whereinall electrodes are electrically insulated one from another and whereinthe several electrodes have adjustment for spaca contact terminal.

the end wall of each section, is a hollow collar,V

the one for the cathode being identiiied by numeral ll and theoppositeone for the selector grid and anode being designated by numerall. The inner ends of these two collars are directed toward each otherwithin chamber 4I and said ends are parallel to .each other and to theend walls of the said chamber. A cathode 2| as previously described withcylindrical flange 22 on a head It of a housing having cylindrical torso24 and legs 25, limited in position by shoulder 26 is carried by collarI8. the cathode, of course,

. having a heater 21 (see Fig. 6)

At the outside of end wall ll having collar 48 is a virtual extension4l* of said collar to which a metallic ring 3| is secured by welding anend margin within said collar, the other end of said ring being Ysealedby the flare portion of re-en-` 3o The other collar Il is traversed atits inner end trant glass stem l0.

by selector grid 32 as in the construction previously described, saidgrid being secured to the collarand situated in parallel spaced relationto the cathode. Within said collar, spaced from the wall thereof andspaced from and parallel to said selector grid 32, is, using the termbroadly. an anode I3 having a metallic stem 34* extending lengthwise ofthe collar and projecting beyond the far end thereof. In the, presentshowing said stem is made longitudinally adjustable, thereby enablingthe anode to be moved toward and away from the selector grid.

Support for the stem Il* is from the resonator end wall Il at theoutside of which protrudes a virtual extension Iil ci collar 49, ametallic ring 3l being welded or otherwise secured to said co1.- lar.The outer end of said ring has a glasscollar 5l sealed thereto and tothe far end of the glass collar is another ring 5I, which in turn hassecured vacuum tight at itsfar end an annulus 'i2 screw threaded at itsoutside and connected vacuum tight at its inside to the said stem by ailexible diaphragm I3. Outside the threaded annulus is an internallythreaded knob Il having an end wall rotatableupon the stem and engaginga shoulder I! formed on the stem. Outward displacement of the knoblongitudinally of 'the stem is prevented by a cap IB held on the saidstem by a set screw or otherwise as found desirable. The outside of saidknob is provided with an insulating covering Il to avoid subjecting theoperator to potential applied to the stem by'way of cap 56 which isconveniently used as In the showing of Figure`4, the end walls 41 forthe resonator body are made movable with respect to the positive grid31. As in the previously described construction. said positive gridextends between the cathode 3| and selector grid 32 parallel thereto andradially outward to the vicinity of the cylindrical side wall of theresonator, andjin this instance is shown projecting between -the facingends of the side wall sections. Capacity coupling between said positivegrid and the resonant is provided. as before. in the form of -cylindrical shells il* spaced each from one said resonator wall section adistance adequate to prevent passage of D. C. potential.` These shellsare coaxial with the respective sections ofthe resonator.Y within whichsituated. and are shown with outturned iianges It* next the .positivegrid, said flanges being-juxtaposed upon and secured to the vsaid gridat its peripheral margin. Support for said grid and shells is obtainedby of radial wires Il, which are introduced through glass seals in thisinstance formed` integrally with a glass ring Il coaxially situatedaround, but-spaced outwardly from the periphery of said positive grid I1and outside and spaced from resonator walll sections 46. At top andbottom edges of this glass ring in virtual continuation thereof aremetallic rings having substantially the same coefiicient of expansion asthe glass ring and preferably of the aforementioned Kovan At' themarginof each said metallic ring Il remote from the marginsealed in theglass, is secured. as by welding. an annulus I0 the outer periphery ofwhich is screw threaded and receives a threaded collar Il, the other endof which is ilanged'inward. as at I2, to overlie the end wall Il of theresonator. The outside of thiscollar 6I is covered with insula'tion B3that it maybe grasped and operated with immunity to electrical shock tothe operator. Between saidannulus Il and end wall 41 afiiexible memberor bellows M is secured vacuum tight, said bellows'preferably exertsreilient pressure longitudinally or axially thereof, thereby tending toseparate the end wall I1 from the annulus when unscrewing the collar 6|.The selector grid mounted on re-entrant collar I! from end wall 4l isthus adjustable with respect to the positive grid I1, and similarlycathode 2l is independently adjustable with respect to said positivegrid. construction accomplishes a support of each ectrode electricallyinsulated from support for all other electrodes.

Whilethe constructions so far described utilize hollow body resonatorswhich are included within the evacuated region, the invention alsocontemplates the use of resonators exterior to the evacuated region.Such a-construction isshown by Figures 7 to 9, wherein theevacuatedregion is confined to a cartridge-like enclosure. As shown, theconstruction is substantially an adap tation of the collars Il and 20 ofFigure l, prov viding a glass seal-.betweenv the collars, said sealsupporting thepositive grid.

Describing the showingofFigures'l to 9 more in detail, axially alignedmetallic collars i6, Il

are provided the facing ends of which are parallel. One of thesecollars, 66,-'su'pportsa cathode 2| in front thereof in accordance withdescriptions heretofore given in connection with constructions of theother ilgures of the drawings, and corresponding reference numerals fromFigure' l are applied without repetition of the description.

Similarly, the other collar 81 hasa" selector grid atits inner-end andcontains an electrode for distinguishing purposes-again called an anode)supported by a stem sealed through al glass dome,

and reference numerals from Figure 1 are again applied withoutrepetition of description. Difference in the collars from the showing ofFigure 1 exists in the provision of radial fianging or enlargement ofsaid collars at 88 inthe vicinity of sealing of the Kovar" rings ll andJ6 thereto. Virtual extensions I9 of said collars project from the saidenlargements in directions away from each other and coaxially to andaround said rings. Projecting toward each other from said enlargementsand situated around said collars are glass rings 10 for insulating andsealing purposes. The outside diameter of these glass rings issubstantially the same as for the extensions 69. A washer-likeconductive plate 1| has its inner margin situated between and sealed tothe contiguous ends of the glass rings 10, said plate extending radiallyoutward from said rings and having an outer peripheral cylindrical rim12 thereon the outer face whereof is screw threaded. 'I'he inner marginof the said plate next the said rings has the positive grid 31 securedthereto, said grid being situated between and parallel to the cathodeand selector grid.

The said collars 66, B1 and their extensions 69 constitute innercylindrical walls for an annular resonator chamber 13, the outer wall ofwhich is composed of cylindrical sections 14 having contiguous endsflanged, as at 15, and seated against plate 1I within rim 12 thereof.Clamping nuts 16 on the said rim engaging the outer flat faces of saidilanges clamp the said sections in axial alignment coaxially to theinner wall of the resonator.

The outer ends of the resonator chamber are closed with insulatingspacers 11. Within the chamber 'I3 next each outer end thereof is aninwardly facing piston 18 having sliding contact with one cylindricalwall of the resonator and having capacitative relation to the othercylindrical wall thereof so as to pass high frequency current butprevent passage of the D, C. low y potential. Arbitrarily we showcontact of the piston with outer wall 14 and capacitative relation towall 69 but this arrangement may be re versed if desired. Each piston iscarried by a plurality of plunger rods 19 which extend outwardly throughthe spaces 11 and are attached to a wheel-like controlling handle y80.An output coupling 44 is provided as before, to take advantage of thegenerated power.

Spacing of the electrodes and constitution of the so-called anode aselectron receiving, reflecting or multiplying may be carried out inaccordance with the disclosure of said concurrently filed application,wherefore specific showing of spac ing of electrodes in Figures 3, 6 and9 herein is to be considered illustrative rather than restrictive.

It will be noted with respect to -all showings herein that special carehas been taken of making parts on opposite sides of the positive gridsas nearly identical as possible, thereby reducing the number ofdifferent parts to be fabricated, and lowering costl of tools, dies andxtures in manufacture of the device.

We claim: f

1. An electronic device comprising a cylindrical outer wall having endwalls, said cylindrical outer wall and end walls forming a hollowenclosure, collars projecting from said end walls toward each otherwithin said enclosure coaxial with said cylindrical outer wall, anelectronpulling electrode within and next the inner end of one of saidcollars and electrically insulated therefrom, a grid iixed to theelectrode-containing collar in spaced parallelism to saidelectronpulling electrode, a second grid parallel to and spaced from thefirst said grid and having a part therefrom projecting radially throughthe said cylinder, and a cathode parallel to and on the opposite side ofthe second grid from the rst grid and axially aligned with saidelectron-pulling electrode for directing electrons through the saidgrids toward said electrode.

2. An electronic device comprising a cylindrical outer wall having endwalls, said outer wall and end walls forming a hollow enclosure, a gridtransverse to said cylindrical outer wall and parallel to said end wallsdividing said enclosure substantially in half and forming the saidenclosure into two resonators, collars projecting from said end wallstoward each other and toward said grid and coaxial to and within therespective resonators and forming innerl cylindrical walls therefor, anelectron-pulling electrode within and electrically insulated from onesaid collar, a cathode carried by the other said collar, andcapacitative coupling in the electrical circuit between said grid andcollar and interposed between said outer cylindrical wall and said innercylindrical walls of each resonator for providing continuity of circuitfor high frequency and interposing thereby interruption to circuit pathfor lowirequency current from said grid to said collars.

3. An electronic device comprising a pair of aligned cylinders, cndwalls at the outer ends of said cylinders, a fixed grid transverse tothe axis of said cylinders and at a plane between inner ends of saidcylinders, said grid having a peripheral portion projecting between saidinner ends of the cylinders, collars coaxial with said cylinders andprojecting toward each other and toward said grirlfrom said end walls, agrid at the inner end of one of said collars, said grids being parallelto eachother, an electron-pulling electrode within the` collar havingthe grid, and a cathode carried by the opposite collar from the onehaving said electrode therein, said cathode having electrical continuitywith the collar carrying the same, and one of the grids havingelectrical continuity with the other of said collar.

4. An electronic device having a cathode and an opposed electron-pullingelectrode and having a hollow body resonator, re-entrant coaxial collarstherein, the inner ends whereof are directed toward each other, saidhollow body resonator comprising an outer shell in electrical continuitywith said collars and providing an inner shell capacitatively coupledwith respect to the outer shell, thereby providing high frequencyelectrical continuity, and a grid physically and electrically joined tothe said inner shell and situated between the said inner ends of there-entrant co'- axial collars. y

5. An electronic device having a cathode and an opposed electron-pullingelectrode and having a hollow body resonator having end walls, meansproviding electrical discontinuity of one end wall to the other, each ofsaid end walls having an outer shell section as part of the resonatorbody and cach having-a re-entrant collar within said shell section, aninner shell capacitatively coupled with respect to both said outer shellsections, and a grid physically and electrically joined to the saidinner shell and situated between the said outer shell sections and saidre-entrant collars out of electrical contact therewith. I

6. An electronic device comprising coaxial collars having ends directedendwise toward each other, one having a cathode at its end and the otherhaving a grid at its end, `said collars each having an enlargementthereon, a second grid' between said ends of the collars, insulatingrings between said enlargements and said second grid supporting saidsecond grid and sealing the in- REFERENCES CITED v The followingreferences are of record in the le of this patent:

Number UNITED STATES PATENTS Name Date Dallenbach Aug. B0, 1938Dllenbach July 25, 1939 Varian et al June 30, 1942 Litton Oct. 13, 1942H8611 May 21, 1946

